include/asm-cris/semaphore.h

   1 /* $Id: semaphore.h,v 1.3 2001/05/08 13:54:09 bjornw Exp $ */
   2
   3 /* On the i386 these are coded in asm, perhaps we should as well. Later.. */
   4
   5 #ifndef _CRIS_SEMAPHORE_H
   6 #define _CRIS_SEMAPHORE_H
   7
   8 #define RW_LOCK_BIAS             0x01000000
   9
  10 #include <linux/wait.h>
  11 #include <linux/spinlock.h>
  12 #include <linux/rwsem.h>
  13
  14 #include <asm/system.h>
  15 #include <asm/atomic.h>
  16
  17 /*
  18  * CRIS semaphores, implemented in C-only so far.
  19  */
  20
  21 struct semaphore {
  22         atomic_t count;
  23         atomic_t waking;
  24         wait_queue_head_t wait;
  25 };
  26
  27 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  28 {                                                                       \
  29         .count          = ATOMIC_INIT(n),                               \
  30         .waking         = ATOMIC_INIT(0),                               \
  31         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  32 }
  33
  34 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  35         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  36
  37 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
  38
  39 static inline void sema_init(struct semaphore *sem, int val)
  40 {
  41         *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
  42 }
  43
  44 static inline void init_MUTEX (struct semaphore *sem)
  45 {
  46         sema_init(sem, 1);
  47 }
  48
  49 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  50 {
  51         sema_init(sem, 0);
  52 }
  53
  54 extern void __down(struct semaphore * sem);
  55 extern int __down_interruptible(struct semaphore * sem);
  56 extern int __down_trylock(struct semaphore * sem);
  57 extern void __up(struct semaphore * sem);
  58
  59 /* notice - we probably can do cli/sti here instead of saving */
  60
  61 static inline void down(struct semaphore * sem)
  62 {
  63         unsigned long flags;
  64         int failed;
  65
  66         might_sleep();
  67
  68         /* atomically decrement the semaphores count, and if its negative, we wait */
  69         cris_atomic_save(sem, flags);
  70         failed = --(sem->count.counter) < 0;
  71         cris_atomic_restore(sem, flags);
  72         if(failed) {
  73                 __down(sem);
  74         }
  75 }
  76
  77 /*
  78  * This version waits in interruptible state so that the waiting
  79  * process can be killed.  The down_interruptible routine
  80  * returns negative for signalled and zero for semaphore acquired.
  81  */
  82
  83 static inline int down_interruptible(struct semaphore * sem)
  84 {
  85         unsigned long flags;
  86         int failed;
  87
  88         might_sleep();
  89
  90         /* atomically decrement the semaphores count, and if its negative, we wait */
  91         cris_atomic_save(sem, flags);
  92         failed = --(sem->count.counter) < 0;
  93         cris_atomic_restore(sem, flags);
  94         if(failed)
  95                 failed = __down_interruptible(sem);
  96         return(failed);
  97 }
  98
  99 static inline int down_trylock(struct semaphore * sem)
 100 {
 101         unsigned long flags;
 102         int failed;
 103
 104         cris_atomic_save(sem, flags);
 105         failed = --(sem->count.counter) < 0;
 106         cris_atomic_restore(sem, flags);
 107         if(failed)
 108                 failed = __down_trylock(sem);
 109         return(failed);
 110
 111 }
 112
 113 /*
 114  * Note! This is subtle. We jump to wake people up only if
 115  * the semaphore was negative (== somebody was waiting on it).
 116  * The default case (no contention) will result in NO
 117  * jumps for both down() and up().
 118  */
 119 static inline void up(struct semaphore * sem)
 120 {
 121         unsigned long flags;
 122         int wakeup;
 123
 124         /* atomically increment the semaphores count, and if it was negative, we wake people */
 125         cris_atomic_save(sem, flags);
 126         wakeup = ++(sem->count.counter) <= 0;
 127         cris_atomic_restore(sem, flags);
 128         if(wakeup) {
 129                 __up(sem);
 130         }
 131 }
 132
 133 #endif